Added support for configuration file

- BASE_PATH is set using the openspace.cfg file. The binary will look
upwards in the directory hierarchy until it is found.
- All other paths is defined in the configurationfile. Paths may be
absolute or relative using the ${BASE_PATH} token
- Moved SGCT configuration files to its own folder
- Updated tests to support new configuration loading

- TODO: Make the loading of configuration easier for the programmer.

src/util/time.cpp

@@ -18,7 +18,7 @@ Time::Time() {
 	time_ = 0.0;
 
 	// load spice time kernel
-	furnsh_c (absPath("${OPENSPACE-DATA}/spice/naif0010.tls").c_str());
+	furnsh_c (absPath("${OPENSPACE_DATA}/spice/naif0010.tls").c_str());
 
 	// convert UTC to ET 
 	str2et_c ( "2006 JAN 31 01:00", &time_ );